The present invention relates to a method for preparing a sintered body of titanium boride and an apparatus which is suitable to carry out the method.
Titanium is a light metal of high toughness with silver gray luster, and it is a metallic element of group IV which with other elements is used as additive for alloys.
Boron, like aluminium, is an element of group III, and it is used as a deoxidizer or degasing reagent in metal refining as it is possesed of a character that it readily reacts with oxygen and nitrogen at high temperature.
The influence of the above mentioned titanium and boron on metal alloy is well-known.
The purpose of titanium and boron addition to metal alloy generally is to give toughness to the metal alloy as in high speed cutting tools disclosed in Franks and Field U.S. Pat. No. 1,684,131 of September 1928, or to enhance a certain property of a metal. Compounds of titanium and boron on the other hand are known to have physical property of good endurance at high temperature, and titanium boride is a representative among them.
The abovementioned titanium boride is a solid of high toughness with its melting point of 2,980.degree. C., and is known as a proper material for electrical conductor at high temperature, for example such as the electrode in aluminium refining apparatus or the electrode in aluminium sputtering apparatus, because of its acid resistance and conductivity under high temperature, and also excellent anticorrosion character against molten aluminium.
These titamium borides are generally produced by hot pressure method wherein the mixture of titanium powder and boron powder are applied to high pressure under temperature of 2,000.degree. C. and above to give the sintered body.
However, the sintered body obtained by this method has problem in that it includes portions of nonhomogeneous density, and that molding an adequate shape which fits to its usage is impossible, so the hot pressed sintered body should undergo the next process, which is to get these portions of nonhomogeneous density eliminated and to be shaped as desired.
Titanium boride is a material of high toughness as well known, and there is a fair amount of difficulty in forming to desired shape.
Besides, the method of simultaneous sintering wherein titanium powder and boron powder is mixed and molded to a desired shape, then the mold is ignited by force to cause the self burning which emits the heat of reaction that will sinter the mold into titanium boride may be adopted to obtain the sintered body by using the character of boron which cause a self burning when subject to high temperature.
However, the density difference between the reactants and the products during the composing process by the self burning in this method will cause plenty of pores in the sintered body as final object constituting its brittle physical property.